Recently, there has been an increased opportunities to do push-type data deliveries like Earthquake Early Warnings, where data is delivered from a server device to a lot of client terminal devices in an emergency. During the delivery, a higher load is imposed on resources of the server device, such as processors, and on a communication network (hereinafter simply called a network) around the server device as data is to be delivered to a larger number of client terminal devices. This higher load may cause a delay in data delivery. If such delay occurs in an emergency, human lives may be involved. Accordingly, an improved infrastructure is needed to ensure that data is delivered without delay even when it is delivered to a large number of client terminal devices. However, such infrastructure improvement is not easy due to cost and other issues. Thus, there is a growing expectation for a technology that allows for data deliveries to a large number of client terminal devices without imposing a heavy load on the server device and network.
As a technique related to such technology, Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2007-274243) discloses a broadcast-type content delivery system using a plurality of channels. This system uses wireless communication to receive content data during a period from the channel switching performed by a user to the connection via wire communication established between a content data delivery device and a terminal device.
Patent Literature 2 (Japanese Registered Patent Publication No. 4696972) discloses a technology involving a plurality of terminal devices that are connected via a hierarchical network. This technology allows delivered content data to be transferred from an upstream terminal device to a downstream terminal device.